Separation strips for photographic plates and method of making such strips



Oct.

12, 1965 A. L. 4vAN DER AUWERA SEPARATION STRIPS FOR PHOTOGRAPHIG PLATES AND METHOD OF MAKING SUCH STRIPS Filed April 24. 1961 m NZ I,

l0 A/o/ls Laurens Van Der Auwera INVENTOR y WWAVTTORNEY United States Patent O SEPARATION STRIPS FOR PHOTOGRAPHIC PLATES AND METHOD OF MAKING SUCH STRIPS Alois Laurens VanDer Auwera, Mortsel, Antwerp, Belgium, assignor to Gevaert Photo-Producten N.V., Mortsel, Belgium, a Belgian company Filed Apr. 24, 1961, Ser. No. 105,854 9 Claims. (Cl. 206-62) These separation strips are fixed at the edge between the photographic plates to prevent a direct contact beltween the plates whereby damaging of the light-sensitive emulsion layer is avoided.

Hitherto separation strips have been made out of paper or cardboard. Such separation strips, however, have the tendency to adopt the widely varying properties of the paper materials from which they are made and to thus adversely affect in a more or less serious way the light sensitive emulsion layer coated on said photographic plates. This detrimental effect appears sometimes after a very short period of time and sometimes after a more extended period, causing fogging, insensitiveness and other defects. Moreover it increases the collection of dust particles on the plates.

To a large degree all these difficulties and defects may be avoided by providing the separation strips with a protective layer which consists of varnish gelatin, z/ein or cellulose compounds etc. Sometimes, however, damage of the light-sensitive emulsion layer has still been noticed.

In order to diminish the risk of damage, the separation strips are reduced in size. Hereby the dimensional stability of these strips becomes insufhcient and their initial shape becomes deformed so that it will be difficult to interpose and to keep these strips in fixed position between the photographic plates. Finally, said separation strips, being provided with the protective lay-ers mentioned hereinbefore, are not entirely moistureproof.

It has now been found that, if these separation strips are made out of polyalkylenes or halogenated polyalkylenes, such as polyvinyl chloride, polyethylene, polypropylene, polytetrafluoroethylene, etc., they are not subject to deformation or to collecting dust particles. Moreover, they do not affect the light-sensitive emulsion layer because of their chemical inert nature and their resistance to moisture.

As an alternative embodiment of the present invention these polyalkylenes or halogenated polyalkylenes can also be applied as a protective layer to the commonly known paper separation strips. Said application can be executed by coating the polyalkylene or halogenated polyalkylene from a suitable solvent, or by fixing and adhering the polyalkylene or halogenated polyalkylene as a thin sheet onto the paper strip by means of direct or high frequency heating. Besides paper some other suitable fibrous base material may be utilized.

According to this alternative embodiment, during or after the separation strips have been shaped to the desired profile, heating may still be practised so that the dimensional stability can still be increased.

On account of their lasting dimensional stability the separation strips according to the present invention may be easily fixed between the photographic plates, and they remain well in place.

An embodiment of the invention is illustrated by way of example in the accompanying drawing in which:

FIG. yl is a cross-section through a set of fou-r photographic plates, the separation strips being inserted between the confronting emulsion coatings of two adjacent plates.

3,211,285 Patented Oct. 12, 1965 FIG. 2 is a cross-section through a set of two photographic plates showing a modified form of separation strip.

FIGURE 3 is a cross-section through a set of two plates showing still another modified form of the separation strip.

In FIG. 1 four photographic plates 1 are represented, positioned two by two, with the light-sensitive emulsion sides 2 arranged to face each other. These light-sensitive emulsion sides of the photographic plates are separated by means of two U-shaped separation strips 3. These separation strips consist of a paper sheet to which a polyethylene sheet or film of 0.07 mm. thickness has been bonded at both sides by high frequency heating. The paper sheet treated in this way is cut into small sheets on bands whereafter these sheets are folded into a U- shape and simultaneously heated. Finally these sheets are cut into short strips.

In FIG. 2. two photographic plates 1 are represented which are packed together in a wrapping folder. The emulsion sides of both photographic plates are turned towards each other for preventing the damaging of the light-sensitive emulsion layer of these photographic plates which may be caused by a pressing or rubbing of the wrapping folder against the subjacent plate surfaces. The plates are separated by two L-shaped polyethylene separation strips. These separation strips consist of a short 1 mm. thick part 4 which is inserted between the plates and a thin part 5 also called a wing part having a thickness of 0.1 mm. resting against the side edge of one of the plates. This thin part 5 is sufficiently flexible to be folded over together with the wrapping folder as shown in the figure.

Finally, an alternative embodiment of the first example illustrated in FIGURE 3, the separation strips according to the present invention can be made either by applying a thin polyethylene protective layer 6 at both sides of a paper sheet or band 7, or by extruding the polyethylene directly on this paper sheet or band. Thereafter said sheet or band is cut into narrow strips of short length and then the strips are L- or U-wise folded.

It will be understood that the accompanying drawings merely illustrate the present invention without limiting the scope thereof, and that other modifications and other synthetic products may be used within the scope of this invention, as defined in the appended claims.

What is claimed is:

1. A stack of photographic plates comprising:

V(a) a plurality of individual photographic plates provided with light sensitive emulsion surface layers,

(b) a separation strip contacting and separating said individual plates,

(c) said separation strip having at least the surfaces thereof which contact the light sensitive emulsion layers of adjacent photographic plates formed of polyalkylene resin.

2. A stack of photographic plates as defined in claim 1 including a plurality of separation strips each of said strips contacting and separating adjacent individual plates.

-3. A stack of photographic plates according to clairn 1 wherein said separation strip has a protective coating of a halogenated polyalkylene resin.

4. A stack of photographic plates according to claim 1, wherein said separation strip has a substantially L-shaped cross-section.

5. A stack of photographic plates according to claim 1 wherein said separation strip has a substantially U-shaped cross-section.

6. A stack of photographic plates according to claim 1 wherein a portion of said separation strip is of reduced thickness and adapted to contact the edges of the photographic plates.

7. A stack of photographic plates according to claim 1 wherein said separation strip has a protective coating of a polyethylene resin.

8. A stack of photographic plates according to claim 1 wherein said separation strip consists of halogenated polyalkylene resin.

9. A stack of photographic plates according to claim 1 References Cited by the Examiner UNITED STATES PATENTS wherein said separation strip consists of a polyethylene 10 EARL M. BERGERT, Primary Examiner.

resin. 

1. A STACK OF PHOTOGRAPHIC PLATES COMPRISING: (A) A PLURALITY OF INDIVIDUAL PHOTOGRAPHIC PLATES PROVIDED WITH LIGHT SENSITIVE EMULSION SURFACE LAYERS, (B) A SEPARATION STRIP CONTACTING AND SEPARATING SAID INDIVIDUAL JPLATES, (C) SAID SEPARATION STIRP HAVING AT LEAST THE SURFACES THEREOF WHICH CONTACT THE LIGHT SENSITIVE EMULSION LAYERS OF ADJACENT PHOTOGRAPHIC PLATES FORMED OF POLYALKYLENE RESIN. 